Calculation of fire resistance of reinforced concrete column by the zone method

This paper describes the calculation of the fire resistance of reinforced concrete column that is exposed to fire from two sides. Calculation of the temperatures has been made depending on whether the heat flow within the reinforced concrete column is one-dimensional or two-dimensional. The temperature of concrete and the temperature of reinforcement are calculated by the Hertz's method. The values of concrete strength and reinforcement, as well as the width of the damage zone of concrete during a certain period of exposure to fire have been calculated. Resistance to the effects of fire on reinforced concrete column has been calculated by the zone method. The time of the resistance of column to the effects of fire has been determined according to the moment capacity of reinforced concrete column

Susceptibility to oxidative stress, insulin resistance, and insulin secretory response in the development of diabetes from obesity

Background/Aim. Oxidative stress plays a critical role in the pathogenesis of various diseases. Recent reports indicate that obesity may induce systemic oxidative stress. The aim of the study was to potentiate oxidative stress as a factor which may aggravate peripheral insulin sensitivity and insulinsecretory response in obesity in this way to potentiate development of diabetes. The aim of the study was also to establish whether insulin-secretory response after glucagonstimulated insulin secretion is susceptible to prooxidant/ antioxidant homeostasis status, as well as to determine the extent of these changes. Methods. A mathematical model of glucose/insulin interactions and C-peptide was used to indicate the degree of insulin resistance and to assess their possible relationship with altered antioxidant/prooxidant homeostasis. The study included 24 obese healthy and 16 obese newly diagnozed non-insulin dependent diabetic patients (NIDDM) as well as 20 control healthy subjects, matched in age. Results. Total plasma antioxidative capacity, erythrocyte and plasma reduced glutathione level were significantly decreased in obese diabetic patients, but also in obese healthy subjects, compared to the values in controls. The plasma lipid peroxidation products and protein carbonyl groups were significantly higher in obese diabetics, more than in obese healthy subjects, compared to the control healthy subjects. The increase of erythrocyte lipid peroxidation at basal state was shown to be more pronounced in obese daibetics, but the apparent difference was obtained in both the obese healthy subjects and obese diabetics, compared to the control values, after exposing of erythrocytes to oxidative stress induced by H2O2. Positive correlation was found between the malondialdehyde (MDA) level and index of insulin sensitivity (FIRI). Conclusion. Increased oxidative stress together with the decreased antioxidative defence seems to contribute to decreased insulin sensitivity and impaired insulin secretory response in obese diabetics, and may be hypothesized to favour the development of diabetes during obesity

THE IMPACT OF WIND INERTIAL AND FIRE BUOYANCY FORCES ON AIR POLLUTION IN STREET CANYON

The air quality has become an important environmental problem worldwide. The pollutants transport in and over urban “street canyons” has attracted great attention due to their negative effects on human health and environment. The aim of this paper is to analyze the impacts of wind and fire on air pollution in a street canyon. For simulations of wind flow and fire plume flow Large Eddy Simulation method of Fire Dynamics Simulator software has been used. Numerical results show that the recirculation flow and the vortices inside the canyon are dependent on a wind inertial force and a fire buoyancy force. The fire buoyancy effect may have a significant impact on the pollutants transport in and over the canyon. For the low wind velocity cases, the dispersion of fire pollutants is controlled by its buoyancy. On the other hand, when the wind effect dominates the buoyancy effect, the pollutants are primarily driven by the wind inertial force. This complex phenomenon affects the pollutant dispersion patterns within many urban streets

Unique function for describing stress and strain behaviour of fire-affected concrete

U radu je predložena jedinstvena analitička funkcija za aproksimaciju EC2 krivulja koje opisuju ovisnost naprezanja i deformacije betona na temperaturama u požaru. Na osnovu predložene funkcije dobivena je familija krivulja koje se razlikuju samo po vrijednosti jednog parametra - maksimalne temperature pri požaru. Prikazani su numerički eksperimenti kojima je dokazano da se jednom funkcijom može opisati ponašanje betona u požaru i predloženi su smjerovi daljnjih istraživanja.A unique analytic function for the approximation of EC2 curves describing dependence of stress and strain of concrete at fire-generated temperatures is presented n the paper. The proposed function enables generation of a family of curves differing only in the value of a single parameter - maximum temperature during fire. Numerical experiments demonstrating that fire behaviour of concrete can be described with a single function are presented, and directions for further study are proposed

Citric Acid Cross-Linked Gelatin-Based Composites with Improved Microhardness

The aim of this study is to investigate the influence of cross-linking and reinforcements in gelatin on the physico-mechanical properties of obtained composites. The gelatin-based composites cross-linked with citric acid (CA) were prepared: gelatin type B (GB) and β-tricalcium phosphate (β-TCP) and novel hybrid composite GB with β-TCP and hydroxyapatite (HAp) particles, and their structure, thermal, and mechanical properties were compared with pure gelatin B samples. FTIR analysis revealed that no chemical interaction between the reinforcements and gelatin matrix was established during the processing of hybrid composites by the solution casting method, proving the particles had no influence on GB cross-linking. The morphological investigation of hybrid composites revealed that cross-linking with CA improved the dispersion of particles, which further led to an increase in mechanical performance. The microindentation test showed that the hardness value was increased by up to 449%, which shows the high potential of β-TCP and HAp particle reinforcement combined with CA as a cross-linking agent. Furthermore, the reduced modulus of elasticity was increased by up to 288%. Results of the MTT assay on L929 cells have revealed that the hybrid composite GB-TCP-HA-CA was not cytotoxic. These results showed that GB cross-linked with CA and reinforced with different calcium phosphates presents a valuable novel material with potential applications in dentistry

Citric Acid Cross-Linked Gelatin-Based Composites with Improved Microhardness

The aim of this study is to investigate the influence of cross-linking and reinforcements in gelatin on the physico-mechanical properties of obtained composites. The gelatin-based composites cross-linked with citric acid (CA) were prepared: gelatin type B (GB) and β-tricalcium phosphate (β-TCP) and novel hybrid composite GB with β-TCP and hydroxyapatite (HAp) particles, and their structure, thermal, and mechanical properties were compared with pure gelatin B samples. FTIR analysis revealed that no chemical interaction between the reinforcements and gelatin matrix was established during the processing of hybrid composites by the solution casting method, proving the particles had no influence on GB cross-linking. The morphological investigation of hybrid composites revealed that cross-linking with CA improved the dispersion of particles, which further led to an increase in mechanical performance. The microindentation test showed that the hardness value was increased by up to 449%, which shows the high potential of β-TCP and HAp particle reinforcement combined with CA as a cross-linking agent. Furthermore, the reduced modulus of elasticity was increased by up to 288%. Results of the MTT assay on L929 cells have revealed that the hybrid composite GB-TCP-HA-CA was not cytotoxic. These results showed that GB cross-linked with CA and reinforced with different calcium phosphates presents a valuable novel material with potential applications in dentistry

FIRE DYNAMICS IN A BUILDING COMPARTMENT – A NUMERICAL STUDY

Building fires heavy pollute the air and jeopardize human health and life. In this paper, the Large Eddy Simulation method of Fire Dynamics Simulator code has been used to investigate the temperature regime and the pollutant concentrations in a compartment and near a building wall under fire scenario. Numerical results show that the generation of fire products in the compartment is largely dependent on the temperature and the quantity of oxygen available for combustion. The outdoor plume parameters are affected by the temperature difference between the fire flame and plume and the surrounding ambient air

3D printing of carvedilol oral dosage forms using selective laser sintering technique

The adjustment of the dose according to the individual needs of the patient is a unique advantage of 3D printing technology, which is of particular importance for the pediatric and geriatric population, due to the diverse needs and characteristics of these groups of patients (Kotta et al., 2018). Selective laser sintering (SLS) is one of the newest 3D printing techniques that uses powder materials, where the powder particles are connected under the influence of laser beams. The main disadvantage of SLS 3D printing is the high process temperature, which can lead to the degradation of active substances. On the other hand, this technique has many advantages, such as high resolution, the possibility of powder recycling and the absence of pre- processing (Fina et al., 2018; Thakkar et al., 2021).14th Central European Symposium on Pharmaceutical Technology, 28th - 30th September, Ohrid, N. Macedonia, 202

A new approach to fire safety system in the process of atmospheric rectification of oil

This paper presents the methods of detection and diagnosis of failures, that is, detecting the existence and causes of failure that can be applied in systems that operate in real time. The proposed system allows automatic and semi-automatic security management, and provides general average or minimizes the consequences of disasters. In addition, it defines the conditions, i.e. the intervals of parameter values, under which causes of failure are created. Based on these parameters, optimal design of protection is possible and it enables the efficient management of the system. Suggested fi re safety system in the process of atmospheric rectification of oil offers the possibility to choose an optimal diagnostic algorithm and its practical and economic usage. A new approach should be applied in order to reduce fire hazards in the process of atmospheric rectification of oil. Fire safety system should be inseparable from the technological process, and vise versa. The procedure recommended for fault detection and diagnosis consists of two phases. The first phase involves the assessment of the process state, while the second involves the identification of the values of processing parameters and their correlation with the process model parameters

CALCULATION OF THERMAL RADIATION LEVEL DURING A POOL FIRE CAUSED BY LEAKAGE OF KEROSENE FROM TANKER WAGON AT RAILWAY CROSSINGS

The spillages due to collisions related incidents involving the wagon tankers, which carrying hazardous materials (hazmat), can be followed by fires or explosions, presents a severe threat to the safety of residents and nearby buildings. In this study, ALOHA and PHAST was used to evaluate the level of thermal radiation at different distances from the place of accident. Discussed scenario analyze a leakage of kerosene from a tanker wagon, from different opening diameters, where is formed a pool fire. As an assumption for location of possible accident, parts of the railway where it can be expected a large number of people and vehicles were taken. For study area was chosen city of Niš, Serbia